A window regulator mechanism using a wire of this kind is disclosed in British Patent No. 1,375,737, where a pair of pulleys rotatably mounted on brackets forms a triangular arrangement together with the drum of a driving portion. A wire wound on the drum is trained around the pulleys and forms a closed loop. In order to open or close the window, the drum is rotated to move the wire, thus elevating or lowering the windowpane joined to the wire. The pulleys are connected to the driving portion via the brackets to which the pulleys are pivotally mounted. This prevents the wire from disengaging from the pulleys. Therefore, the window regulator mechanism using the wire is mounted in a door having a window while maintaining the triangular arrangement. Thus, an excessively large access hole is formed in an inner door panel to permit the mounting operation. The window regulator mechanism is introduced into the door through this hole, and then the regulator mechanism is rigidly attached to the door. Consequently, the large hole makes it impossible to place components to be mounted to the inner door panel, such as an inside door handle and an armrest, in their optimum positions. Further, the large size of the access hole reduces the mechanical strength. Thus, if the door is closed violently, the inner door panel is depressed.